> There is no requirement that you pair an EQ_PERIODIC with an EQ_TRIGGER. Take for exmaple
> 
>   midas/examples/experiment/frontend.cxx
> 
> and remove there the triggered event. The frontend runs happily with the periodic event only (I just tried that myself). You have probably some problem in 
> your event definition. Start with the running example frontend, and add your code line by line until you see the problem.

Hi Stefan, thank you very much! 

As the pointer to the readout function and pointers to device drivers are all defined in the same structure (EQUIPMENT), 
I was naively assuming that the readout function should be set during the class driver initialization.
Now it is clear that the equipment responding to EQ_PERIODIC events doesn't have to have drivers, 
and specifying the readout function is the responsibility of the user.

I got around exactly this way yesterday, but was thinking that I was hacking the system :)
 
-- regards, Pasha

Dear MIDAS experts, 

I have a question about "tmfe approach" to implementing MIDAS frontends. If I read the code correctly, 
within this approach it is the TMFeEquipment things, not the TMFrontend's themselves, 
which handle the run transitions - the TMFrontend class 

https://bitbucket.org/tmidas/midas/src/423082fb67c7711813fcda61f7cd03784c398f49/include/tmfe.h#lines-306:378

simply doesn't have methods to handle those directly. 

So how does a user control the sequence in which TMFeEquipment::HandleBeginRun functions of different 
TMFeEquipment pieces are called at begin run? - there are two cases to consider: TMFeEquipment things 
defined by the same TMFrontend and by different TMFrontend's.

Many thanks and happy holidays to everyone! 

-- regards, Pasha
 

Hi K.O., your clarification is much appreciated! 
"
> I am not sure what you are trying to do. It is always easier to suggest a solution to a specific problem.

I think, I owe you an explanation :) :

Consider ~ 40 nodes with two FPGAs (PCIE cards) per node, talking to the detector hardware. 
One of those FPGAs, in addition to reading the data, performs the global timing synchronization.
The high-bandwidth data readout is not controlled by MIDAS, so all frontends perform only 'slow control'-type functions.
In MIDAS language, an FPGA implements two different units of slow control equipment: 
one - configuring and controlling a single FPGA (equipment type A), and another one - synchronizing 
multiple FPGAs (equipment type B). On one of the nodes, unit A and unit B share the FPGA card, 
so they better be controlled by the same frontend. 

For one, I need to make sure that all type A equipment units, managed by multiple frontends, 
are initialized before the [single] type B unit which shares the frontend with the type A unit. 
And, of course, the end of a run transition has to be handled in the opposite order - type B unit 
shuts down first. 

As 'periodic' actions for all registered pieces of equipment are performed in the same loop [thread], 
registering the equipment in the needed order - first A, then B - should give a solution - thanks for making that clear.     

> 
> 1) "time ordering of run transitions" - of course midas transitions are ordered by transition sequence numbers 
> and the tmfe class provides methods to control this. ditto for the mfe.cxx frontends.
> 
> 2) for one TMFrontend, the order of calling HandleBeginRun() is the order in which equipments were added to the 
> equipment using FeAddEquipment(). HandleEndRun() is called in reverse order. (I better check this).

the ordering of the rpc handler calls in tmfe's tr_stop/tr_pause/tr_resume functions is ok.

> 
> 3) to have multiple TMFrontends in one program would be unusual (mfe.cxx frontends completely do not support 
> this), but should work. Everything was coded to support this, but it was never tested in practice because we 
> cannot invent any useful use-case for it. HandleBeginRun() handlers are likely to be called in the frontends are 
> created. (I could check this and confirm it works, as long as you have a valid use-case for this configuration).

agreed, I don't think there is a good use case for that, so no need to spend time checking.

> 
> 4) Frontend X has EquipmentA and EquipmentB, you want EqA::HandleBeginRun() to be called at run transition 200 
> and EqB::HandleBeginRun() to be called at run transition 400.
> 
> This is not directly supported by mfe.cxx frontends (the begin_run() handler is a global function) and I did not 
> directly implement it in the TMFE frontend.
> 
> But I think this would be a useful improvement. I will look into this. 

In the simplest case, registering the equipment units in the right order is definitely the answer. 
However a single FPGA can perform multiple logically independent tasks and thus represent 
multiple logical units of equipment. Those units however are not independent: they share the hardware (FPGA) 
and thus do depend on each other. Giving users a full control over the sequence in which those logical units 
execute their run transitions is quite likely to be needed, for example, to work around peculiarities of the 
custom-made kernel drivers.
 
> 
> Likely I will add per-equipment data members fEqConfBeginRunSeqNo, fEqConfEndRunSeqno, etc. Value 0 would 
> unregister the corresponding run transition handler. This would cleanup the code quite a bit, a bunch
> of RegisterTranstionXXX functions could go away.

this also makes sense. -- thanks again, regards, Pasha

> 
> K.O.

Dear MIDAS experts,

I'm using MIDAS javascript interface (mjsonrpc) to communicate with a frontend from a custom web page 
and observe that the if the frontend's response exceeds certain number of bytes, it is always truncated. 

MIDAS C/C++ RPC interface allows users to specify the max response length :

https://daq00.triumf.ca/MidasWiki/index.php/Remote_Procedure_Calls_(RPC)#C++_2

How would one do the same from with mjsonrpc ? 

-- many thanks, regards, Pasha

Dear MIDAS experts,

I have a time series of slow control measurements in an ASCII format - 
data records in a format (run_number, time, temperature, voltage1, ..., voltageN), 
and, if possible, would like to convert them into a MIDAS history format. 

Making MIDAS events out of that data is easy, but is it possible to preserve 
the time stamps?  - Logically, this boils down to whether it is possible to have  
the event time set by a user frontend

-- as always - many thanks, regards, Pasha

I think I found an answer to my question: a user-controlled event header does have a time stamp: 

https://daq00.triumf.ca/MidasWiki/index.php/Event_Structure#Event_Header

-- apologies for the spam, regards, Pasha

> I have a time series of slow control measurements in an ASCII format - 
> data records in a format (run_number, time, temperature, voltage1, ..., voltageN), 
> and, if possible, would like to convert them into a MIDAS history format. 
> 
> Making MIDAS events out of that data is easy, but is it possible to preserve 
> the time stamps?  - Logically, this boils down to whether it is possible to have  
> the event time set by a user frontend

It looks that the original question was not as naive as I expected and may be pointing to a subtle bug. 
I have implemented a python frontend - essentially a clone of 

https://bitbucket.org/tmidas/midas/src/develop/python/midas/frontend.py

reading the old slow control data and setting the event.header.timestamp's to some dates from the year of 2022. 

When I run MIDAS and read the "old slow control events", one event in 10 seconds, 
the MIDAS Event Dump utility shows the data with the correct event timestamps, from the year of 2022. 

However the history plots show the event parameters with the timestamps from Feb 01 2025 and the adjacent 
data points separated by 10 sec.

Is it possible that the history system uses its own timestamp setting instead of using timestamps from the event headers? 
- Under normal circumstances, the two should be very close, and that could've kept the issue hidden... 

-- thanks, regards, Pasha

UPDATE:  I attached the frontend code and the input data file it is reading. The data file should reside in the local directory
- the frontend code doesn't have everything fully automated for the test, 
  -- an integer field "/Mu2e/Offline/Ops/LastTime" would need to be created manually
  -- the history plots would need to be declared manually

Dear MIDAS experts, 

I confirm that when writing out history files corresponding to the slow control event data, 
MIDAS history system timestamps the data not with the event time coming from the event data, 
but with the current time determined by the program - 

https://bitbucket.org/tmidas/midas/src/293d27fad0c87c80c4ed7b94b5c40ba1e150bea4/progs/mlogger.cxx#lines-5321

where 'now' is defined as  

time_t now = time(NULL);

I'm looking for a way to timestamp the history data with the event time - that is important 
for HEP applications outside the DAQ domain. Yes, MIDAS infrastructure is very well suited for that, 
there could have a number of such applications, and experiments could significantly benefit from that.

So I'm wondering whether the implementation is a design choice made or it could be changed. 

The change itself and especially its validation may require a non-negligible amount of work - I'd be happy to contribute.

Any insight much appreciated. 

-- thanks, regards, Pasha

 I once looked at using LUA for this,
> but I think basing off an full featured programming language like python
> is better.

if it came to a vote, my vote would go to Lua: it would allow to do everything needed, 
with much less external dependencies and with much less motivation to over-use the interpreter. 
The CMS experience was very teaching in this respect... 

-- my 2c, regards, Pasha

> You can always include your "true" data timestamp as the first value in your data.

Are you saying that if the first data word of a history event were a timestamp, 
the MIDAS history system, when plotting the time dependencies, would use that timestamp 
instead of the mlogger timestamp?  

if that is true, what tells MIDAS that the first data word is the timestamp? 

I couldn't find a discussion of that on the page describing the history system - 

 https://daq00.triumf.ca/MidasWiki/index.php/History_System#Frontend_history_event

- perhaps I should be looking at a different page?

-- thanks again, regards, Pasha 

Dear MIDAS experts,

does the ODBXX interface to ODB currently ODB links in the path names? - From what I see so far, it currently fails to do so,
but I could be doing something else wrong... 

-- thanks, regards, Pasha

it is a very convenient interface! Does it support the ODB links in the path names ? -- thanks, regards, Pasha

Dear All, 

I'm pretty sure many know this already, however I found this feature by a an accident 
and want to share with those who don't know about it yet - seems very useful. 

- it looks that one can use ROOT scripting with rootcling and call from the 
  interactive ROOT prompt any function defined in midas.h and access ODB seemingly 
  WITHOUT DOING anything special 

- more surprisingly, that also works for odbxx, with one minor exception in handling 
  the 64-bit types - the proof is in attachment. The script test_odbxx.C loaded 
  interactively is Stefan's

 https://bitbucket.org/tmidas/midas/src/develop/examples/odbxx/odbxx_test.cxx 

with one minor change - the line 
 
   o[Int64 Key] = -1LL;

is replaced with

   int64_t x = -1LL;
   o["Int64 Key"] = x;

- apparently the interpeter has its limitations. 

My rootlogon.C file doesn't load any libraries, it only defines the appropriate 
include paths. So it seems that everything works pretty much out of the box. 

One issue has surfaced however. All that worked despite my experiment 
had its name="test_025", while the example specifies experiment="test". 
Is it possible that that only first 4 characters are being tested ? 

-- regards, Pasha

Dear MIDAS experts, 

I'm running into a minor but annoying issue with the subdirectory name ordering by the ODB browser. 
I have a straw-man hash map which includes ODB subdirectories named "000", "010", ... "300", 
and I'm yet to succeed to have them displayed in a "natural" order: the subdirectories with names 
starting from "0" always show up on the bottom of the list - see attached .png file. 

Neither interactive re-ordering nor manual ordering of the items in the input .json file helps. 

I have also attached a .json file which can be loaded with odbedit to reproduce the issue. 

Although I'm using a relatively recent - ~ 20 days old - commit, 'db1819ac', is it possible 
that this issue has already been sorted out ?

-- many thanks, regards, Pasha  

Dear MIDAS experts, 

currently, the MIDAS messaging system is optimized for one-line long messages, 
so the content of 2+liners shows up in the message log in the reverse order, 
with the first line on the bottom of the message. 

I wonder if printing the message content in the reverse order, starting from the last line, 
would make sense ? - that wouldn't affect one-line long messages, but could make longer 
messages more useful. 

--thanks, regards, Pasha

perhaps c++20? - std::format is an immediately useful feature. --regards, Pasha

> Following discussions at the MIDAS workshop, we propose to move MIDAS from c++11 to c++17. There is 
> many new features and we want to start using some of them.
> 
> Per my previous message https://daq00.triumf.ca/elog-midas/Midas/3084,
> c++17 is available on current MacOS, U-22 and newer, el9 and newer, D-12 and newer.
> 
> (ROOT moved to C++17 as of release 6.30 on November 6, 2023)
> 
> As I reported earlier, MIDAS already builds with c++23 on U-24, and this move does not require any 
> actual code changes other than a bump of c++ version in CMakeLists.txt and Makefile.
> 
> Please let us know if this change will cause problems or if you think that we should move to an older 
> c++ (c++14) or newer c++ (c++20 or c++23 or c++26).
> 
> If we do not hear anything, we will implement this change in about 2-3 weeks.
> 
> K.O.

> > perhaps c++20? - std::format is an immediately useful feature. --regards, Pasha
> 
> confirmed. std::format is an improvement over K&R C printf().
> 
> but seems unavailable on U-20 and older, requires --std=c++20 on U-24 and MacOS.

agreed! - availability is significantly more important. -- regards, Pasha

Dear MIDAS experts,

when I attempted to increase the max number of hotlinks in ODB , defined as 

#define MAX_OPEN_RECORDS       256           /**< number of open DB records   */

I started running into an assertion in midas/src/odb.cxx

https://bitbucket.org/tmidas/midas/src/fa5457b5274a6b42c5ed8b6dea5e3cdd43de38fe/src/odb.cxx#lines-1525 :

  assert(sizeof(DATABASE_CLIENT) == 2112);

is it possible that the size of the DATABASE_CLIENT structure should be checked against 64+sizeof(OPEN_RECORD)*MAX_OPEN_RECORDS ?
- 64 clearly can be expressed in a better maintainable form  

UPDATE: similar consideration holds for the size of the DATABLE_HEADER structure, which is also checked against a constant

https://bitbucket.org/tmidas/midas/src/fa5457b5274a6b42c5ed8b6dea5e3cdd43de38fe/src/odb.cxx#lines-1526

-- many thanks, regards, Pavel

 

I see - thank you for the explanation!  

Indeed, updating MIDAS clients on each and every RPI etc in a running experiment may be a real challenge. 

Thinking forward - would it help if the ODB clients, upon initial connection but before doing anything else 
were reading the ODB parameters from the ODB itself, so the clients were "learning" about the ODB structure 
dynamically, at run time? Or that knowledge has to be static ?

-- thanks, regards, Pavel

> I wonder why one needs more than 256 hotlinks at all. Please note that with the odbxx "watch" API, you can hotline a whole subdirectory, and get notified if ANY of the 
> underlying values or subdirectories change. In principle, one could have one hotlink to "/" and see all changes in the ODB (although that does not make sense and might slow 
> down ODB access a bit).

Thanks ! - I didn't know that. I did run into a number of hotlinks limit via mlogger which complained about not being able to create a hotlink 
to yet another event. Doubling the default value of MAX_OPEN_RECORDS solved the problem. 

I don't know the exact arithmetic defining the number of hotlinks in the system, but my today's case is a case of 
- 36 (linux servers) +18 (RPI) monitoring frontends managing one or several different equipment items each. 
- Each equipment item sends to ODB at least one monitoring event 
- in addition, each frontend created an individual hotlink for handling interactive commands 
- for MAX_OPEN_RECORDS=256, 4 equipment items per frontend easily make it into the dangerous zone. 

"Equipment items" also include the online processes running on the distributed computing farm processing the data .. 
(we are not using MIDAS event building capabilities)
 
> 
> Try the odbxx_test.cpp example in MIDAS. In line 210 it puts a single hotlink to /Experiment. If you change anything under /Experiment, the program gets notified. By checking the 
> path of the changed ODB entry, it can figure out which of the subways have been changed:
> 
>    // watch ODB key for any change with lambda function
>    midas::odb ow("/Experiment");
>    ow.watch([](midas::odb &o) {
>       std::cout << "Value of key \"" + o.get_full_path() + "\" changed to " << o << std::endl;
>    });
> 
> 
> Maybe that would solve your problem without having to change the maximum number of hotlinks.

I'll see how much mileage one can make here, but so far it looks that it is the number of various monitoring events 
handled by the mlogger which  drives the number of hotlinks 

-- thanks, regards, Pavel